Modern light sources of cars focus on the light performance, style and appearance, as well as on modern technologies such as LED sources, etc. Due to this fact, the design of these elements is gradually becoming more complex and complicated.
The power supply, or control of LEDs (Light Emitting Diodes), is one of the main tasks of the development of electronic systems. For the power supply of individual LEDs or LED chains or LED arrays, current power supply units are generally used. Some functions use a sophisticated system of switching of individual elements in the lamp to ensure a more attractive appearance, and better functionality. One of these functions is progressive switching of LEDs to provide an animated direction indicator.
For the control of progressive switching, several system concepts and architectures are commonly used, which are described below.
Switching of individual LEDs by means of special circuits is one of the most frequently used solutions. A DC/DC converter (direct current converter) implemented as a current power supply unit is used, the LED board containing a dedicated circuit that is able to switch on or off individual LEDs at given intervals based on a command. These circuits can ensure control of all functions—detection, timing, and switching, or can control just a partial function, e.g. switching, with the other functions being controlled by an LDM (LED drive module). A disadvantage of such a solution is the necessity to provide a complicated interface between the LED board and the LDM, and typically includes a high cost, with an advantage being its relatively easy use and implementation.
Another known solution consists in switching and control of LEDs by means of a u-controller controlling (switching) each LED individually. In this case, a DC/DC converter is also implemented as a current power supply unit. A disadvantage of such a solution is a complicated interface between the LED board and the LDM, and the necessity to use a u-controller with a sufficient number of outputs.
Another known variant is implementation of the progressive function by means of discrete components without using a u-controller. For the power supply, a DC/DC converter is also used, and LEDs are switched individually by means of transistors. For the generation of time constants, RC circuits are used (e.g., circuits of resistors and capacitors). Disadvantages include its complexity, not quite sufficient wiring reliability, and inaccurate timing, while an advantage may be a lower price.
The attached FIG. 1 shows an example of a known design of the light function in a car lighting application, such as a headlamp or a rear lamp. The apparatus consists of the main connector 1′, an LDM power supply unit 2′, a connecting interface 3′ and a LED board 4′ containing light emitting diodes and switching electronic components. The main connector 1′ represents the input electronic interface of the lamp. The light control unit (BCM) provides the respective light functions via the car cabling and the main connector of the lamp. The LED board 4′ contains components for the control of switching and generation of light, with the LED board controlling functions including headlights, meeting lights, daylights, etc. LDM 2′ is an electronic part responsible for the power supply of the LED light sources. The interface 3′ provides interconnection between LDM 2′ and the LEDs 4′.